1. Field of the Invention
The present invention relates to a honeycomb structured body.
2. Discussion of the Background
In recent years, particulates such as soot and the like contained in exhaust gases discharged from internal combustion engines of vehicles, such as buses and trucks, and construction machines, have raised serious problems as those particulates are harmful to the environment and the human body.
There have been proposed various honeycomb structured bodies made from porous ceramics, which serve as filters capable of collecting particulates in exhaust gases to purify the exhaust gases.
Conventionally, with respect to the honeycomb structured body of this type, a filter having the following structure has been proposed: two kinds of through holes, that is, a group of through holes with a relatively large capacity (hereinafter, referred to as large-capacity through hole) and a group of through holes with a relatively small capacity (hereinafter, referred to as small-capacity through hole), are prepared, and each of the large-capacity through holes is sealed with a plug at one end, and each of the small-capacity through holes is sealed with a plug at the other end. With respect to the honeycomb structured body of this type, there has been proposed a technique in which the opening side of the large-capacity through holes is used as the inlet-side of a filter with the opening side of the small-capacity through holes being used as the outlet-side of the filter (for example, see JP-A 56-124418, JP-A 56-124417, JP-A 62-96717, J UM-A 58-92409, U.S. Pat. No. 4,416,676, JP-A 58-196820, U.S. Pat. No. 4,420,316, JP-A 58-150015, JP-A 5-68828, French Patent No. 2789327, International Publication No. WO02/100514, International Publication No. WO02/10562, and International Publication No. WO03/20407).
Moreover, there have been known honeycomb structured bodies (such as filters) having a structure in which the number of through holes that have openings on the inlet-side (hereinafter, referred to as inlet-side through holes) is made greater than the number of through holes that have openings on the outlet-side (hereinafter, referred to as outlet-side through holes), and the like (for example, see FIG. 3 of JP-A58-196820).
In the honeycomb structured bodies of this type, the through holes are constituted by two types of through holes, that is, a group of large-capacity through holes (having a relatively great total amount of surface areas and cross-sectional areas) and a group of small-capacity through holes (having a relatively small total amount of surface areas and cross-sectional areas).
Recently, in the case where the honeycomb structured body is used in an exhaust gas purifying device as a filter, processes to carry out oxidizing and removing of particulates, together with processes to carry out purifying (converting) of toxic gas components in exhaust gases through oxidation and reduction are adopted, by allowing the honeycomb structured body to support a catalyst.
The contents of JP-A 56-124418, JP-A 56-124417, JP-A 62-96717, J UM-A58-92409, U.S. Pat. No. 4,416,676, JP-A58-196820, U.S. Pat. No. 4,420,316, JP-A 58-150015, JP-A 5-68828, French Patent No. 2789327, International Publication No. WO02/100514, International Publication No. WO02/10562, and International Publication No. WO03/20407 are incorporated herein by reference in their entirety.